The image immediately above is a 100% blowup from an images taken on my Sony A7r + 16-35mm FE f/4 lens, processed from raw in Iridient Developer and upsized to 52MP and a 148MB file. Now I don't know about you but I think that's pretty impressive.
In answer to the question at the top of the post, Is this medium-format quality? the answer to that is no. Medium-Format is Medium-format and is about pixel size as much as it is about the number of pixels. And also because using my Sony A7r is a lot easier than using a Medium Format camera anyway. Even if could afford one, I'd be disinclined to use one those heavyweight and clumsy devices anyway. Not exactly the ideal camera for what I do. Plus considering what I can get from the samples above, why would I need MF anyway?
It's just over a year since I got my Sony A7r and I'm still blown away by the images I can create with it. While I don't always want that level of reproduction, there are times when I feel the need to create the best possible images that I can, in terms of reproduction size and quality. And apart from the Nikon D800 series, there is nothing else in the DSLR / Mirrorless world that comes close.
Iridient Developer and what it does is definitely the icing on the cake here. My A7r files were sharp and highly resolved anyway. IR takes this on and also gives me the ability to upsize the files as well. And while they may not be genuine MF quality, they are pretty close and in terms of reproduction who would see the difference anyway.
Since writing this post, I've been out again with this combination and shot some tripod-mounted images at ISO 50, which have to be seen to be believed. Pressure of work has meant that I haven't got round to doing some serious editing on those yet, but when I do I'll post some samples of what I shot and some raw files you can download as well.
In terms of my 'system' camera it's becoming clear that Sony FE has moved to the top of my list in terms of cameras I choose for my bread and butter work. The main reason for this being the quality of the files I can produce. And there really is nothing to beat the A7r, 16-35mm and Iridient Developer combination I am using at the moment. Certainly the best quality image files I have ever created and a pleasure to edit. And the words pleasure and edit don't occur in my sentences about my work very often!!